<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style type="text/css">
        .one, .two {
            width: 200px;
            height: 200px;
            background-color: pink;
        }
        .one {
            margin-bottom: 100px;
        }
        .two {
            margin-top: 200px;
        }
        /* 只有200px，不是300px */
    </style>
</head>
<body>
    <div class="one">
        一
    </div>
    <div class="two">
        二
    </div>
</body>
</html>